Flooring material and method of making same



Patented Jan. 7, 1936 UNITED STATES FLOORING MATERIAL AND METHOD OFMAKING SALIE Herman William Richter, Bridgewater, Mass/' No Drawing.Application May 4, 1931, Serial No. 535,088

4 Claims.

This invention relates to flooring material and particularly to thattype of flooring material that is suitable for use wherever the floorsare subjected to extremely severe service conditions 5 and/or exposureto unusual or marked temperature and atmospheric changes. Suchconditions are met with in factories, railroad stations, pavements, shipdecks, elevators, loading platforms, docks and laboratories. However,mymaterial is not limited to industrial uses and may well be used forpurely domestic purposes.

Prior to the present invention, it was well known that leather, paperstock, or combinations of the two, reduced to fibers and remanufacturedso as to expose the fiber ends to form the wear ing or tread surfaceproduced a flooring having a remarkable durability, elasticity andnon-conductivity .of heat and electricity as well as excellent sounddeadening qualities. However,

practical difilculties were encountered in the manufacture of thismaterial and the product, besides being unattractive in appearance,lacked uniformity and sufiicient waterproofness.

The primary object of this invention is to provide a thoroughlypractical and commercial method for making a flooring material of thisgeneral type.

Another object is to produce a flooring material having all thedesirable attributes of previously developed materials of this generaltype without their accompanying undesirable properties.

Further objects and aims of the present invention, more or less specificthan those referred to hereinabove, will be, in part obvious and in partpointed out in the course of the following description.

Stated in very general terms, my process consists of the followingoperations or sub-processes; namely; (1) preparing a substantiallywaterproof fibrous material in the form of sheets; (2) laminating aplurality of said sheets to form a block; and (3) cutting said block toform flooring slabs.

Leatherboard, or heeling board, as the material is very often termed, isusually made from a furnish composed principally of leather scrap orwaste by board making processes which involve disintegration in abeating engine and subsequent formation into sheets on a wet machine.

As thus prepared, the materialhas very many desirable qualities,including marked durability or wear resisting properties, making itsuitable for use as a flooring material of the end grain type, but it isfar from being water resistant or waterproof. Its water resistingproperties can.

however, be greatly increased by impregnation with waterproofing agents,including asphalts. Such impregnation may be carried out with or withoutthe use of heat and/or pressure or vacuum. 5 I prefer for practicalreasons to incorporate the waterproofing material into the board insitu; i. e. during an intermediate stage of the board making process, sothat there exists a-more intimate bond between the fiber of the boardand 10 the waterproofing agent. Thus, I have found it possible toproduce a board so resistant to water that 'a'sample strip thereofhaving a cross section of 2 inches by .170 of an inch in thickness willabsorb not more than 4.5% to 8.5% of 15 water on being completelyimmersed for as long as 48 hours. Such a board is eminently suitable fora flooring material, especially since the water absorption of a properlylaid flooring is considerably less than that of a block of the same ma-20 terial because of the more favorable relation of surface to .volume.

A typical furnish which I have found suitable in practice consists ofthe following:

Pounds 25 Mixed paper 1200 Leather or leatherboard chips 241 Red oxideof iron 1445 Sodium silicate 98 30 50% clay dispersed asphalt 2845 Themixed papers and leather and/or leatherboard chips are thrown into thebeater first, then the iron oxide, then the sodium silicate and finallythe asphalt emulsion. The iron oxide is used 35 merely as a filler andmay be substituted in whole or in part by any other suitable material.For reasons to be pointed out later, I prefer in certain variations ofthe process to use a n0n-con-' ducting filling material such as Celite,which is a 40 brand of diatomaceous earth. The sodium silicate serves asa conditioner, raising and maintaining the pH, thereby stabilizing theemulsion. The asphalt is the preferred waterproofing material.

After the furnish is thoroughly mixed and in- 45 corporated in thebeater, sufiicient alum or other The sheets are prepared for laminatingby drying, preferably in a tray drier and a subsequent heat or fluxingtreatment at about 220 F. for about two hours. The drying step itselfmay be without heat, in which case the temperature is raised 'to thefiuxing temperature after the drying is completed. The fiuxing may becarried out in the tray drier or in a hot box to which the sheets may betransferred. The sheets, while still hot, are calendered betweencalender rolls and their thickness regulated by the proper adjustment ofthe gap between the rolls. The calender rolls need not be heated.

A possible variation consists-in performing the fiuxing operation in aheated platen press. Another alternative step is to transfer the sheetsfrom the drier or hot box while still in the thermoplastic state to acold press for a quick "bump. Both of these deviations render thecalendering step unnecessary.

The sheets are then cooled, trimmed to desired size, coated with anadhesive and laminated to build up a block of predetermined thickness.The blocks formed in this manner are subjected to pressure to bring thelaminations into intimate contact, the pressure being maintained as longas found necessary in order that the adhesive may properly set.

The blocks are then sawed into slabs. This operation is preferablyperformed with a saw tipped with tungsten carbide. The edges of the slabmust be trued so that they are parallel and the ends are finally clippedoff to give them the desired length (ordinarily 18 inches). The slabscan be given a fine polish by simply rubbing them with a felt fabric orcloth. In actual practice, a felt buffing wheel may be used for thispurpose.

In order to obtain a flooring slab that will not buckle, it has beenfound by actual experiment that the slab should contain from 1 to 1.5%moisture. If a slab containing considerably more than 1.5% water (testswere made with slabs containing 2.5% to 3% water) is cemented to a steelbacking and allowed to remain at ordinary temperatures, the evaporationof the moisture from the exposed surface will cause an uneven shrinkagethrough the block and an accompanying concaving of the exposed surfacesuflicient to bend the steel plate. The opposite effect is observed if abone dry sample is made up in the same way. In this case the slightabsorption of water causes the exposed surface to expand with a convexbowing of the exposed surface and a corresponding bending of the steelplate. If, however, about 1% of moisture is left in the slab, asubstantial equilibrium between the atmosphere and the block seems toresult and no bowing at all takes place.

The waterproofness of the slab and the percentage of residual watercontained therein may be controlled within close limits by the use ofsuitable adhesives and suitable methods of applying the adhesives andlaminating the board. I have, therefore, found it possible to produce awaterproof flooring slab containing about 1% of moisture, which, aspointed out above, is the ideal condition.

Experiments with various adhesives, including casein glues, modifiedstarches, silicates of soda and asphalt, indicate clearly that theadhesive selected must be water resisting. The difficulty with aqueousglues, including starches, silicates and casein glues, is that theynecessarily introduce water into the block. To all intents and purposesthis water is sealed in and even after months of ageing the block isstill quite wet.

When the block is sawed into slabs, this moisture evaporates morereadily and shrinkage naturally takes place. The slab must, therefore,be dried before the finishing operations to prevent the shrinkage.

Another disadvantage of aqueous adhesives is that the water in theseadhesives weakens the board structurally so that during the sawingoperation a separation occurs in the block not at the glued joint butclosely adjacent thereto. The same result is observed when testing theply adhesion of fiber boards by methods in use in the board industry,wherein the board sample is cemented with sodium silicate between blocksof wood and then subjected to strain in a plane perpendicular to theplane of the board. This loosening of plies, in the case of flooring,results in excessive damage in the subsequent edge planing or truingoperation previously referred to.

It is possible to get away from the dimensional instability andlamination-loosening caused by the use of aqueous adhesives and at thesame time eliminate the troublesome drying step by using "non-aqueousadhesives such as asphalts.

Several methods of applying the asphalts were developed, some of whichgive better results than others.

One method is to apply hot asphalt of 160 F. melting point, more orless, and not too low penetration, to one or both sides of each sheet,and then press the cold sheets firmly together to cause them to adhere.The bond is satisfactory, but the floor slabs made from the blocks arenot sufficiently rigid and it seems likely that the low melting point ofthe asphalt may cause extrusion to take place if the flooring issubjected to high temperatures such as that of concentrated sunshine. Ahydrolene asphalt produced by the Sun Oil Company has provedsatisfactory for the bonding operation.

The use of high melting point asphalt (200 to 210 F. melting point) wasresorted to but on account of greater hardness of the adhesive, it wasfound necessary to warm the sheets before laminating them.

A suitable technique is to heat the sheets in an oven, coat them withmolten asphalt, return to oven to restore heat, and finally press themtogether after removing from oven.

Experiments with cold pressing of harder asphalts produced bonds thatwere not wholly satisfactory.

Good results were obtained by coating sheets with thin layers of hardertypes of asphalts, moistening the surfaces thereof with suitablesolvents such as gasolene or carbon tetrachloride and finally pressingthem together firmly.

Good results were also obtained by coating the sheets with hard asphaltsthat had been plasticized with plasticizers or solid solvents such asnaphthalene, halowax (chloronaphthalene) etc.

Though very good results are obtainable with hot asphalts, there arepractical difficulties that make it necessary to turn to methods ofapplying asphalt at ordinary temperatures. Hot asphalt can be handledonly with great difficulty and hazards to workers. Furthermore,expensive equipment is necessary.

Several practical methods of applying asphalts at ordinary temperatureshave been developed. One method consists in applying the asphalt insolution and evaporating the solvent to a predetermined point so thatwhen the sheets are pressed together, the asphalt is moist enough tocause adhesion. The effect is similar to that produced by moistening anasphalt coated sheet with a solvent. Suitable solvents as pointed outpreviously are carbon tetrachloride and gasolene.

A variation of this method consists in evaporatingall of the solvent andheating the sheets to give the asphalt sufilcient plasticity to causethe piled sheets to adhere.

The objections to methods employing a solvent are that most solvents areexpensive and inflammable, and recovery systems are cumbersome andlikewise expensive, both in installation and maintenance.

Excellent methods have been developed in which the asphalt is applied inthe form of an emulsion or dispersion. The emulsion may be appliedbymeans of a roll or brush coating machine, by dipping or by spraying. Thespraying method is the one that is preferred on account of itscomparative simplicity. In any event most of the water must begotten ridof, as was found necessary in case of the aqueous adhesives.

One method consists in preheating the sheets before applying theemulsion, depending upon the heat contained in the sheets to evaporatethe 7 water. It was found possible to so control the process that therewas sufilcient residual heat left in the sheets after the water'had beenevaporated to produce a satisfactory weld between the sheets. '-Thismethod may be termed the residual heat method.

A better method is not to depend upon the residual heat but to put backinto the sheets sufficient heat to increase the plasticity and perfectadaptation of the adhesive. In either case it is necessary to selectasphalts of suitable characteristics such as melting point andpenetrability.

The temperature to which the sheets are heated will depend upon thesecharacteristics.

The results of many experiments indicate that any method which involvesputting back heat into a sheet which has been previously preheated toevaporate the water of the emulsion or heating the sheet to a relativelyhigh temperature throughout is open to serious objection. Sheets offiberboard made as previously described are thermoplastic and, almostrubbery in nature when hot. If pressure is applied to a block of suchsheets, there is grave danger of compressing the block too much. .Toogreat densiflcatlon increases basic weight of fioor, decreasing coverageand thus increasing the cost per square foot. Furthermore, highlycompressed fibrous material is considerably more dimensionally unstablethan a fibrous material of loose texture and will expand much more onbeing immersed on water. 0n the other hand, insufficient pressure willproduce a poor bond.

A method that is much more efiective and practical than any so fardescribed consists in coating cold sheets of fiberboard with an asphaltemulsion and then passing them through a heated zone to dry andsuperficially heat the sheets. This step may be carried out in an ovenat a relatively high temperature. ing renders the asphalt plastic enoughfor an excellent weld, but the main bulk of the board is not heatedthrough and is therefore not in a plastic state. Reasonably highpressures may, therefore, be utilized without densifying the board to anobjectionable degree. In order to further decrease the amount of heatthat reaches the main portion of the board, the iron oxidefiller may besubstituted, as has already been stated, in whole or part by means of anon-conducting filler such as diatomaceous earth. The use of Thesuperficial heatadd to the commercial practicability of the new flooringmaterial as the abrasive action of iron oxide on cutting tools is thesource of much annoyance.

' fillers other than iron oxide will in many cases A further advantageof superficial heating is that since the total amount ofheat put intothe sheet is not great, the final temperature of the must be keptconfined between caui boards by means of retaining clamps.

However carried out, the methods of applying the asphalt by means of anemulsion has the advantage that the thickness of the film of adhesivecan be completely controlled. It is, therefore, possible to produce anadhesive film so thin as to entirely eliminate the unsightly adhesivelines so characteristic of prior flooring materials of the same generaltype. Furthermore, as is well known in gluing practice, the thinner theadhesive film, the better the bond.

Tests have indicated the blocks made with aqueous adhesives run as highas 2.5 to 3.5% of moisture. Blocks bonded with hot asphalt run as low as0.3 and 0.4% moisture. As has been pointed out, the ideal condition isto leave about 1% moisture in the block to obviate buckling. It ispossible to control the drying of a block bonded with hot asphalt toleave this essential amount of water. When asphalt emulsions are used asthe bond, the amount of moisture retained by the block is about 1% sothat the procedures outlined result in a material having thecharacteristics necessary for a non-buckling flooring.

The. flooring material made as described can be simply and inexpensivelyinstalled over any solid sub-floor. If necessary, the underfloor shouldbe properly resurfaced and levelled. A layer of asphalt cement, or othersuitable adhesive, is first troweled over the sub-floor and the slabsare laid therein in a manner similar to brick or tile laying. The slabsshould be pushed tightly together but no great pressure is necessary. Inthis manner there is produced an end-grained flooring that is durable,resilient, water and fire resisting, sound deadening, insulating,dustless I and self-healing.

The foregoing constitutes the essential and distinctive thought of mynew process, but it is to be understood that while I have gone intoconsiderable detail and utilized certain specific terms and language,the present disclosure is illustrative rather than restrictive, and thatchanges and modifications may be resorted to without departing from thespirit and scope of my invention. Furthermore, it is to be distinctlyunderstood that the essence of my invention may be combined with variousother steps and details without affecting the peculiar results obtained.

I claim:-' 1. A method of laminating a plurality of shee consisting inapplying an emulsion containing asphalt to the surfaces to be bonded,passing each sheet through a heated zone to dry and soften the asphaltwithout substantially raising the temperature of the body of the sheetsand uniting said sheets with the application of pressure alone.

2. A method of laminating a plurality of sheets consisting in preheatingeach of the sheets, applying an asphalt emulsion to the surfaces to beunited and pressing said sheets together without further heating, thepreheating being sufiicient to evaporate substantially all of the waterof the emulsion and to produce a weld between the pressed sheets.

3. A method of producing a laminated substantially waterproofleatherboard substantially devoid of a tendency to buckle, whichconsists in fabricating a plurality of sheets of substantiallywaterproof leatherboard from a furnish containing asphalt in the form ofan emulsion or dispersion, coating each of the sheets with a nonaqueousadhesive in the form of an emulsion or dispersion, heating the sheets todrive ofi the water of the emulsion or dispersion and pressing thesheets together.

4. A method of producing a laminated substantially waterproofleatherboard substantially devoid of a tendency to buckle, whichconsists in fabricating a plurality of sheets of substantiallywaterproof leatherboard from a furnish containing asphalt in the form ofan emulsion or dispersion, coating each of the sheets with asphalt inthe form of an emulsion or dispersion, heating the sheets to drive offthe water of the emulsion or dispersion and pressing the sheetstogether.

HERMAN WILLIAM RICHTER.

